Key takeaways:
Low heart rate, or bradycardia, means a heart rate below 60 beats per minute (bpm). But a low rate isn’t always a sign of a problem.
If you’re not having symptoms, then bradycardia may not be a cause for concern. Sometimes, it can even be a sign of good cardiovascular fitness.
There are some important symptoms and concerns you can look out for to know if you should see a healthcare professional for your low heart rate.
With smartwatches and fitness tracking devices gaining popularity, people are aware of their minute-to-minute heart rate more than ever. At times, you might notice that your heart rate seems a little slower than usual. Sometimes, that can be normal. But in some situations, it could be a sign of trouble that requires medical attention.
Let’s take a closer look at what you need to know about low heart rates — also known as bradycardia — and when you need to be concerned enough to seek medical attention.
What is considered a normal heart rate?
Heart rate is the number of times your heart beats per minute (bpm). Normal heart rate can vary due to age, fitness level, and other factors. A normal resting heart rate ranges between 60 bpm and 100 bpm.
What is bradycardia?
Bradycardia is the medical term for a heart rate that’s under 60 bpm. Even though this has a technical medical term, it doesn’t mean bradycardia is always a problem. In some cases, a low heart rate can be normal and healthy or a sign of good physical fitness.
If you have a heart rate under 60 bpm, you should let a healthcare professional know. They can help you figure out if this is a normal heart rate for you.
What is a dangerously low heart rate?
A heart rate under 50 bpm may be dangerously low for many people. In cases of severe bradycardia, the heart may not be able to pump blood and oxygen to vital organs. A low heart rate can be a sign of a more serious medical condition — both in and outside the heart. And this is when bradycardia tends to cause more symptoms.
What are the symptoms of bradycardia?
If you have a resting heart rate in the 50s because you’re physically fit, it’s unlikely that you’ll have any symptoms. Some elite athletes may even dip down into the 40s from time to time — although that’s unusual. When you have a low heart rate from physical fitness, the heart rate will naturally increase when you need it to pump a little harder, like with exercise.
But if your heart rate is abnormally slow for other reasons, it’s more likely that you’ll feel the effects of decreased blood flow. You may experience:
Unexplained fatigue
Dizziness or lightheadedness
Shortness of breath
Poor exercise tolerance
What are common causes of low heart rate?
It’s normal for your heart rate to fluctuate throughout the day. It naturally responds to what your body needs and what you’re doing. Some harmless causes of bradycardia include:
Sleep: Your heart rate is generally lower during sleep or relaxation.
Physical fitness: Cardiovascular activity strengthens your heart muscle. And a stronger heart can pump blood more efficiently. This means that someone who works out regularly is likely to have a lower resting heart rate.
Medications: Some medications lower the heart rate. Some examples include blood pressure medications, like beta blockers or calcium channel blockers. These medications are often prescribed for people whose heart rates are too fast.
While these causes of bradycardia are expected, there are some medical conditions that can also cause a low heart rate.
What other conditions cause a low heart rate?
Many of the medical conditions that cause bradycardia are more common in people who are older or have underlying heart conditions. Below are some examples of the more common medical problems that can cause bradycardia.
Arrhythmia
An arrhythmia refers to any condition that involves a problem with the heart’s electrical pathways. There’s a special electrical circuit in your heart that controls each heartbeat. And problems with this system can cause the signal to go awry.
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Arrhythmias can be fast, but they may also be slow. And some people have both problems. This becomes more common as you get older. Some examples of common arrhythmias include:
Atrial fibrillation (AFib)
Atrial flutter
Heart block
Cardiomyopathy
The general term for problems with the heart’s structure is called cardiomyopathy. And there are many different kinds. This is because the shape and size of your heart can change in response to other medical problems. Cardiomyopathy can be caused by:
Coronary artery disease
Heavy alcohol use
Heart surgery
Congenital heart defects
Hypothyroidism
Hypothyroidism is when the thyroid doesn’t make enough thyroid hormone. It can happen for several different reasons. But no matter the cause, low thyroid is a common cause of a slow heart rate. Correcting the problem will usually bring the heart rate to normal
Electrolyte abnormalities
Electrolytes refer to the different substances in your blood that your cells need to work properly. Examples include:
Sodium
Potassium
Calcium
Magnesium
And changes in your electrolytes can affect your heart rate. For example, dangerously high potassium levels or high calcium levels can slow the heart rate.
Most of the time, your kidneys adjust your electrolytes to keep everything in balance. So abnormal electrolyte levels are uncommon causes of a low heart rate. A simple blood test will reveal if there’s a problem.
Eating disorders
Anorexia can affect your heart rate, making it run too fast or too slow. So can bulimia, if it leads to the serious electrolyte abnormalities we just discussed.
Lyme disease
Lyme disease can affect the heart, but this is rare. It happens to about 1% of people with the infection. Fortunately, most people get better with treatment.
Should you worry about a low heart rate and see a healthcare professional?
When a drop in your heart rate is natural and harmless, it doesn’t cause any symptoms. But if you also have any of the symptoms that we mentioned earlier, it could be a sign that something else is going on.
Even if you don’t have any symptoms, it’s a good idea to talk with a healthcare professional if you have new bradycardia and one of the following conditions:
Being age 50 or older
Heart disease
Kidney disease
A history of electrolyte abnormalities
Thyroid problems
A heart rate below 40 bpm — which is considered dangerously low
There are some simple and easy tests that a healthcare professional can do to figure out if your heart rate is a problem. To start the work-up, you’ll probably get an electrocardiogram (ECG) and blood tests, including thyroid and electrolyte levels.
A healthcare professional may also recommend you wear a small heart monitor for a few days. This gives an exact reading of your heart rate, including the time of day. Some monitors can be kept on for weeks at a time.
Is it dangerous to have a heart rate below 40 while sleeping?
If your heart rate drops under 40 bpm while you’re asleep, it may not be a problem — especially if it doesn’t do this while you’re awake during the day. But it’s still a good idea to see a healthcare professional. They can check for the possible causes of a low heart rate that we already mentioned.
Until devices like smartwatches became widely available, most people never thought much about their heart rate while sleeping. But now that you can monitor your pulse 24 hours a day, you may notice that it can drop quite a lot while you’re asleep.
When you’re sleeping, your parasympathetic nervous system takes over. The parasympathetic system is sometimes called the “rest and digest” system. It tends to lower your blood pressure and heart rate — and that’s normal. Some people will even briefly dip below 50 bpm.
One important cause of a low heart rate during sleep is sleep apnea. A sleep test can tell you if you have sleep apnea. And treating the problem may improve your heart rate and prevent more serious complications for the future.
Treatments for low heart rate
The treatment for a low heart rate partly depends on what’s causing the problem.
For causes that are temporary or reversible — like a medication or an abnormal electrolyte — the treatment is to address the underlying cause.
If you have low heart rate due to a heart condition — like heart block or heart failure — then you may need long-term treatment. The main treatment for a low heart rate is a device called a pacemaker. This is a small, implantable device that can help control the heartbeat.
There are many different types of pacemakers. They’re placed in the chest near the heart during a relatively simple and quick procedure. Once the pacemaker is in place, it doesn’t cause any pain when it’s pacing the heart.
Not everyone who has a low heart rate from a heart condition needs a pacemaker. If your heart rate isn’t dangerously low or causing any symptoms, you and your cardiologist may be able to simply monitor your condition.
Frequently asked questions
You don’t necessarily need to go to the emergency room (ER) if your heart rate is 55 beats per minute (bpm). If you’re having bradycardia along with symptoms like dizziness, shortness of breath, or chest pain, you should seek emergency medical treatment. ER healthcare professionals can determine what’s causing the episode and help safely manage it.
No, dehydration doesn’t usually cause a low heart rate. Dehydration causes the amount of fluids circulating in the circulatory system to decrease. Your heart tries to overcome this deficit by pumping harder and faster. Typically, your heart rate increases with dehydration.
You don’t necessarily need to go to the emergency room (ER) if your heart rate is 55 beats per minute (bpm). If you’re having bradycardia along with symptoms like dizziness, shortness of breath, or chest pain, you should seek emergency medical treatment. ER healthcare professionals can determine what’s causing the episode and help safely manage it.
No, dehydration doesn’t usually cause a low heart rate. Dehydration causes the amount of fluids circulating in the circulatory system to decrease. Your heart tries to overcome this deficit by pumping harder and faster. Typically, your heart rate increases with dehydration.
The bottom line
In healthy and active people, a resting heart rate in the 50s (beats per minute) may be a sign of good heart health. And when this is the case, the bradycardia doesn’t cause any symptoms.
But if a slow heart rate is new for you, or if you’re experiencing symptoms of dizziness, fatigue, or lightheadedness, then it’s time to get a checkup. If you have a fainting episode, then urgent attention in an emergency room is often required. A healthcare professional can order testing to sort out the cause of the problem.
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References
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